import {Vector3} from '../../three.module.js';


/**
 * Generates 2D-Coordinates in a very fast way.
 *
 * Based on work by:
 * @link http://www.openprocessing.org/sketch/15493
 *
 * @param center     Center of Hilbert curve.
 * @param size       Total width of Hilbert curve.
 * @param iterations Number of subdivisions.
 * @param v0         Corner index -X, -Z.
 * @param v1         Corner index -X, +Z.
 * @param v2         Corner index +X, +Z.
 * @param v3         Corner index +X, -Z.
 */
function hilbert2D(center = new Vector3(0, 0, 0), size = 10, iterations = 1, v0 = 0, v1 = 1, v2 = 2, v3 = 3) {

  const half = size / 2;

  const vec_s = [
    new Vector3(center.x - half, center.y, center.z - half),
    new Vector3(center.x - half, center.y, center.z + half),
    new Vector3(center.x + half, center.y, center.z + half),
    new Vector3(center.x + half, center.y, center.z - half)
  ];

  const vec = [
    vec_s[v0],
    vec_s[v1],
    vec_s[v2],
    vec_s[v3]
  ];

  // Recurse iterations
  if (0 <= --iterations) {

    const tmp = [];

    Array.prototype.push.apply(tmp, hilbert2D(vec[0], half, iterations, v0, v3, v2, v1));
    Array.prototype.push.apply(tmp, hilbert2D(vec[1], half, iterations, v0, v1, v2, v3));
    Array.prototype.push.apply(tmp, hilbert2D(vec[2], half, iterations, v0, v1, v2, v3));
    Array.prototype.push.apply(tmp, hilbert2D(vec[3], half, iterations, v2, v1, v0, v3));

    // Return recursive call
    return tmp;

  }

  // Return complete Hilbert Curve.
  return vec;

}

/**
 * Generates 3D-Coordinates in a very fast way.
 *
 * Based on work by:
 * @link https://openprocessing.org/user/5654
 *
 * @param center     Center of Hilbert curve.
 * @param size       Total width of Hilbert curve.
 * @param iterations Number of subdivisions.
 * @param v0         Corner index -X, +Y, -Z.
 * @param v1         Corner index -X, +Y, +Z.
 * @param v2         Corner index -X, -Y, +Z.
 * @param v3         Corner index -X, -Y, -Z.
 * @param v4         Corner index +X, -Y, -Z.
 * @param v5         Corner index +X, -Y, +Z.
 * @param v6         Corner index +X, +Y, +Z.
 * @param v7         Corner index +X, +Y, -Z.
 */
function hilbert3D(center = new Vector3(0, 0, 0), size = 10, iterations = 1, v0 = 0, v1 = 1, v2 = 2, v3 = 3, v4 = 4, v5 = 5, v6 = 6, v7 = 7) {

  // Default Vars
  const half = size / 2;

  const vec_s = [
    new Vector3(center.x - half, center.y + half, center.z - half),
    new Vector3(center.x - half, center.y + half, center.z + half),
    new Vector3(center.x - half, center.y - half, center.z + half),
    new Vector3(center.x - half, center.y - half, center.z - half),
    new Vector3(center.x + half, center.y - half, center.z - half),
    new Vector3(center.x + half, center.y - half, center.z + half),
    new Vector3(center.x + half, center.y + half, center.z + half),
    new Vector3(center.x + half, center.y + half, center.z - half)
  ];

  const vec = [
    vec_s[v0],
    vec_s[v1],
    vec_s[v2],
    vec_s[v3],
    vec_s[v4],
    vec_s[v5],
    vec_s[v6],
    vec_s[v7]
  ];

  // Recurse iterations
  if (--iterations >= 0) {

    const tmp = [];

    Array.prototype.push.apply(tmp, hilbert3D(vec[0], half, iterations, v0, v3, v4, v7, v6, v5, v2, v1));
    Array.prototype.push.apply(tmp, hilbert3D(vec[1], half, iterations, v0, v7, v6, v1, v2, v5, v4, v3));
    Array.prototype.push.apply(tmp, hilbert3D(vec[2], half, iterations, v0, v7, v6, v1, v2, v5, v4, v3));
    Array.prototype.push.apply(tmp, hilbert3D(vec[3], half, iterations, v2, v3, v0, v1, v6, v7, v4, v5));
    Array.prototype.push.apply(tmp, hilbert3D(vec[4], half, iterations, v2, v3, v0, v1, v6, v7, v4, v5));
    Array.prototype.push.apply(tmp, hilbert3D(vec[5], half, iterations, v4, v3, v2, v5, v6, v1, v0, v7));
    Array.prototype.push.apply(tmp, hilbert3D(vec[6], half, iterations, v4, v3, v2, v5, v6, v1, v0, v7));
    Array.prototype.push.apply(tmp, hilbert3D(vec[7], half, iterations, v6, v5, v2, v1, v0, v3, v4, v7));

    // Return recursive call
    return tmp;

  }

  // Return complete Hilbert Curve.
  return vec;

}

/**
 * Generates a Gosper curve (lying in the XY plane)
 *
 * https://gist.github.com/nitaku/6521802
 *
 * @param size The size of a single gosper island.
 */
function gosper(size = 1) {

  function fractalize(config) {

    let output;
    let input = config.axiom;

    for (let i = 0, il = config.steps; 0 <= il ? i < il : i > il; 0 <= il ? i++ : i--) {

      output = '';

      for (let j = 0, jl = input.length; j < jl; j++) {

        const char = input[j];

        if (char in config.rules) {

          output += config.rules[char];

        } else {

          output += char;

        }

      }

      input = output;

    }

    return output;

  }

  function toPoints(config) {

    let currX = 0, currY = 0;
    let angle = 0;
    const path = [0, 0, 0];
    const fractal = config.fractal;

    for (let i = 0, l = fractal.length; i < l; i++) {

      const char = fractal[i];

      if (char === '+') {

        angle += config.angle;

      } else if (char === '-') {

        angle -= config.angle;

      } else if (char === 'F') {

        currX += config.size * Math.cos(angle);
        currY += -config.size * Math.sin(angle);
        path.push(currX, currY, 0);

      }

    }

    return path;

  }

  //

  const gosper = fractalize({
    axiom: 'A',
    steps: 4,
    rules: {
      A: 'A+BF++BF-FA--FAFA-BF+',
      B: '-FA+BFBF++BF+FA--FA-B'
    }
  });

  const points = toPoints({
    fractal: gosper,
    size: size,
    angle: Math.PI / 3 // 60 degrees
  });

  return points;

}


export {
  hilbert2D,
  hilbert3D,
  gosper,
};
